1. Field of the Invention
This invention relates to ultrasonic wave diagnosing apparatus, more particularly, to an ultrasonic wave diagnosing apparatus scanning three-dimensional ultrasonic waves.
2. Description of Related Art
There are already invented various ultrasonic wave probes which are well-known can be inserted into body cavities to obtain cross-sectioned images within the bodies. Such conventional ultrasonic wave probes typically have a display by means of such single scanning systems as a linear scanning system or a radial scanning system.
However, in the case of observing plaque or the like within a vein, it is desirable to take a three-dimensional image by simultaneously displaying a linear image and a radial image.
Therefore, there is a conventional a method wherein, as shown in FIG. 33(A), by advancing and retreating in each rotation an ultrasonic wave probe 301 having an ultrasonic wave oscillator 302 in one side part, several cross-sectioned images are taken in and processed to display linear images and radial images.
For such an apparatus wherein radial images and linear images can be obtained, an apparatus wherein an ultrasonic wave probe can be made to radially scan and can be moved in the axial direction is disclosed in the publications, for example, of Japanese patent application laid open No. 9439/1982 and Japanese utility model application laid open No. 74108/1988.
Another known scanning system for simultaneously displaying a radial image and a linear image is a spiral system wherein, as shown in FIG. 33(B), the probe 301 is advanced and retreated at any time and is simultaneously rotated.
The present applicant has also suggested, in the publication of Japanese patent application laid open No. 265536/1990, such apparatus wherein the rotating drive and advancing and retreating drive of an ultrasonic wave probe are synchronized with each other to be controlled as is shown in FIGS. 34 and 35.
In a three-dimensional scanning driving part 310 of a prior art example, as shown FIG. 34, an ultrasonic wave oscillator 311 used for transmitting and receiving an ultrasonic wave is connected to a shaft-like drive transmitting part 312, and both are contained within a sheath 313 closed in a spherical tip part. The above-mentioned sheath 313 is provided within its tip a sealing member 314 and O-rings 315 holding the above-mentioned drive transmitting part 312. The space within the tip part of the sheath 313, which is tightly sealed with the above-mentioned sheath 313, sealing member 314 and O-rings 315, is filled with an acoustic medium 316.
The above-mentioned drive transmitting part 312 in the rear end part is extended out of the rear end part of the above-mentioned sheath 313 and is connected to a stepping motor 318 through a connecting part 317. This stepping motor 318 is combined with an encoder 319 detecting the rotating position of the stepping motor 318 and they are both contained and held within a rotating motion part sheath 320.
The above-mentioned rotating motion part sheath 320 is fitted to an advancing and retreating motion transmitting part 321 which is screwed to an advancing and retreating mechanism part 322 consisting of a ball screw. The above-mentioned advancing and retreating mechanism part 322 is connected to a stepping motor 323 driving part so as to be rotated by this stepping motor 323. The above-mentioned stepping motor 323 is combined with an encoder 324 for detecting the rotating position of this stepping motor 323.
The above-mentioned connecting part 317, stepping motor 318, encoder 319, rotating motion part sheath 320, advancing and retreating motion transmitting part 321, advancing and retreating mechanism part 322, stepping motor 323 and encoder 324 are enclosed with the sheath 325 to which is fixed the above-mentioned sheath 313 in a rear end part. The above-mentioned stepping motor 323 is fixed to the above-mentioned sheath 325.
As shown in FIG. 35, the ultrasonic wave probe controlling system comprises a controlling circuit 330 controlling the rotation, advancing and retreating of the ultrasonic wave oscillator 311, a clock oscillator 331 inputting a starting signal str of the ultrasonic wave oscillator 311 and outputting a clock clc, and a delaying circuit 332 inputting the clock clc from the above mentioned clock oscillator 331 and outputting a signal DLY obtained by delaying this clock clc by 1/4 period T.
The above-mentioned clock clc and signal DLY are input as two-phase driving signals into the stepping motors 318 and 323 through a switching switch 333, which is controlled by a controlling signal J from the above-mentioned controlling circuit 330 to switch the state where the clock clc is of a phase A and the signal DLY is of a phase B and the state that the clock clc is of the phase B and the signal DLY is of the phase A over to each other.
The phase A, output C of the encoder 319 connected to the above-mentioned stepping motor 318 and the phase Z, output Z output in each rotation are input into the above mentioned controlling circuit 330. In the same manner, the phase A output G and phase Z output H of the encoder 324 connected to the above mentioned stepping motor 323 are input into the above-mentioned controlling circuit 330.
However, even if spiral scanning is made with such three-dimensional ultrasonic wave diagnosing apparatus, a three-dimensionally scanned ultrasonic wave image will be able to be observed only at the time of scanning. In order to process images accurately three-dimensionally by using a computer or the like on the basis of the ultrasonic wave image obtained by the three-dimensional scanning, it is necessary to record the images once at regular intervals in some image recording means.
In order to prepare frame memories as required for the three-dimensional scanning within the ultrasonic wave diagnosing apparatus body, for example, in order to record 200 sheets of an ultrasonic wave image formed of 512.times.512.times.8 bits, a recording capacity of 40M bits will be necessary. In order to prepare such a volume of frame memories, a large amount of expensive memories will be required, the ultrasonic wave diagnosing apparatus body will have to be large, the power consumption will be large and the heat generation will be large.
It has also been impossible to continuously memorize images of a plurality of disease examples.
Further, in order to improve the insertability of the above mentioned ultrasonic wave probe into a body cavity, the probe is desired to be small in its outside diameter. For example, in Japanese utility model application laid open No. 141421/1990, there is disclosed an ultrasonic wave probe wherein a member (housing) holding an ultrasonic wave oscillator unit is made slidably adjacent to the sheath inside diameter surface to make the outside diameter of the probe small.
However, in the above-described ultrasonic wave probe wherein the housing holding the ultrasonic wave oscillator unit is made adjacent to the sheath inside diameter surface to make the probe outside diameter small, the case of a structure that an ultrasonic wave transmitting medium for transmitting ultrasonic waves is compactly closed within the sheath, there will be such disadvantages that the above-mentioned housing will act the same as a piston, where the ultrasonic wave transmitting medium between the probe tip and the above-mentioned housing will obstruct the movement in the lengthwise direction of the above mentioned housing and the linear scannability will deteriorate.
In such a case, if the tip of the ultrasonic wave probe is opened in the structure, the above-described disadvantages will be able to be avoided but, in the ultrasonic probe opened at the tip, there will be such fears that a body liquid will enter the probe interior, the sterilizability will deteriorate and the interior structure of such a probe, including the ultrasonic wave oscillator unit, will contact the living body to reduce the electric insulatability.
Now, in the ultrasonic probe scanning system, there are an electronic scanning system and a mechanical scanning system. The ultrasonic wave beam scanning form can be sectioned into a digital system and a linear system.
FIG. 36(a) shows a radial system ultrasonic wave probe A, and FIG. 36(b) shows a linear system ultrasonic wave probe B. In the drawings, the reference numeral 407 represents an ultrasonic wave oscillator and 406 represents a sheath.
An ultrasonic wave probe of a mechanical linear scanning system is disclosed in the publication, for example, of Japanese patent application laid open No. 302836/1988.
The formation of a conventional mechanical linear scanning system ultrasonic wave probe apparatus shall be explained with reference to FIG. 37.
This ultrasonic wave probe apparatus comprises an ultrasonic wave probe 402 to be inserted into a human body 401, a driving part 403 making this ultrasonic wave probe 402 scan ultrasonic wave beams, an ultrasonic wave observing means 404 building an image signal from a received signal and a television monitor 405 depicting an image.
In the above-mentioned ultrasonic wave probe 402, the reference numeral 406 represents a long flexible sheath containing an ultrasonic wave oscillator 407 reciprocatable within its tip. A flexible shaft 408 within this sheath 406 transmits a reciprocating motion generated by the above-mentioned driving part 403 to the above-mentioned ultrasonic wave oscillator 407 to reciprocate this ultrasonic wave oscillator 407 to linearly scan ultrasonic wave beams.
Within the above-mentioned driving part 403, the rotary motion of a motor 409 is converted to a reciprocating motion by a converting mechanism 410, and this reciprocating motion is transmitted to the above mentioned flexible shaft 408. An encoder 411 detects the rotation angle displacement of the motor 409 and, on the basis of this detected result, controls the reversal of the rotating direction, controls the rotation of the motor 409 and corrects the turbulence of an image 405a caused by the rotation dispersion of the motor 409.
In the case of a diagnosis, the above-mentioned ultrasonic wave probe 402 is inserted into an objective position 412 (for example, a total bile duct) within the human body 1. When the above-mentioned ultrasonic wave oscillator 407 is reciprocated by the driving part 403, an ultrasonic wave beam transmitted and received by this ultrasonic wave oscillator 407 will be linearly scanned to obtain a received signal. This received signal is transmitted to the ultrasonic wave observing means 404 and is converted to an image signal.
Then, this image signal is transmitted to the television monitor 405 and, as shown in FIG. 38(a), an ultrasonic wave cross-sectioned image of the position where the ultrasonic wave beam has been scanned will be depicted.
In FIG. 39, the reciprocating motion generated by the driving part 403 and the reciprocating motion of the ultrasonic wave oscillator 407 reciprocated through the flexible shaft 408 are shown along a time series.
As the above mentioned flexible shaft 408 unavoidably extends and contracts, it will contract in the strokes (a) to (c) where the driving part 403 pushes the ultrasonic wave oscillator 407 but will extend in the strokes (e) to (g) where the above-mentioned ultrasonic wave oscillator 407 is pulled.
Therefore, in the strokes (d) and (h) where the push/pull is reversed, though the above-mentioned driving part 403 is moving, the above mentioned ultrasonic wave oscillator 407 will stop for a moment.
However, in the ultrasonic wave observing means 404, an image signal is built as synchronized with the rotation displacement of the motor 409 of the driving part 403 by the signal of the encoder 411, image flows will be produced in the part where the above-mentioned ultrasonic wave oscillator 407 stops in the ultrasonic wave cross-sectioned image displayed on the monitor 405, that is, as shown in FIG. 38(b), in both end parts of the image 405a.
Thus, in the conventional ultrasonic wave probe apparatus, there have been such problems that no faithful ultrasonic wave cross-sectioned image will be obtained and the diagnosis will be greatly obstructed.
As a counter-measure against them, the movement displacement of the ultrasonic wave oscillator 407 may be directly detected in the tip part of the above-mentioned ultrasonic wave probe 402, it is technically impossible to make the encoder so small as to be able to be mounted within the small diameter ultrasonic wave probe 402.
There is also considered a means of transmitting the image signal to the television monitor 405 from the ultrasonic wave observing means 404 with the signals in both end parts of the image 405a cut but there are problems that the position of the image contents will be different in the going path and returning path of the scanning and, as shown in FIGS. 40(a) and (b), the image 5a will seem to rock to the right and left with the reciprocation of the ultrasonic wave oscillator 407.
As described above, there have been such problems that, by conventional techniques the image flows in both end parts of the image 405a can not be effectively removed and the disadvantages in the diagnosis cannot be solved.